Need help to using matrix to solve.

[oceanhow]

Can anyone pls help to solve the solution set of the system of equations given above, where a, b, c are unknowns.

w+5x+6y-z=a
2w+2x+2z=b
-2w-x+y=c

And is the system overdetermined or underdetermined?

 

[HallsofIvy]

You have three equations in four unknown variables. What do you think?

 

[oceanhow]

You have three equations in four unknown variables. What do you think?

yes, i know that got three equations in four unknowns variables.
So in the question is want to solution with matrix, but i don't know how to start and end the result.
Can u help me?